1. Field
One or more embodiments of the present disclosure relate to an apparatus for detecting an oil level and a method for controlling the same, an apparatus for detecting oil flow and a method for controlling the same, and a method for controlling oil return using the detected oil level and the detected oil flow.
2. Description of the Related Art
A compressor has a structure in which a compression assembly to suction and compress a refrigerant is disposed in an upper part of a casing and an electric assembly is disposed in a lower part of the compression assembly. In this case, the compression assembly and the electric assembly share one rotation shaft, the rotation shaft is rotated based on power generated by the electric assembly and the compression assembly coupled to the rotation shaft is operated through such rotation, thus causing compression.
In this case, supply of oil to bearings, scrolls and the like of the compression assembly is required to facilitate rotation of the compression assembly. Oil is stored in an oil storage portion disposed in a lower part of the casing, and is then supplied to the compression assembly. The oil performs lubrication actions and contributes to cooling of the electric assembly, and control of stable supply of an appropriate amount of oil stored in the compressor is needed.
In order to maintain the appropriate amount of oil in the compressor, an oil level stored in the compressor must be confirmed, and normal operation and appropriate control of the oil return system must be achieved.
However, as configurations of the compressor gradually become more complicated and compressors are used for air-conditioning systems (e.g., a system air-conditioner, multi-air conditioner, etc.), pipes in which oil and working fluids flow are increased in length and control of oil levels in the compressors thus gradually becomes more difficult. In particular, as pipe length increases, an amount of residual oil in pipes increases and the amount of oil stored in the oil storage portion is irregularly and greatly changed during operation although an appropriate amount of oil is supplied in an early stage.
For this reason, there is a need for continuously or periodically checking the oil level in the oil storage portion. Conventionally, the oil level is not confirmed, and the oil return operation is performed at intervals of a predetermined time irrespective of the oil level. However, in this case, the oil return operation is mandatorily performed even when a sufficient amount of oil is present in the oil storage portion, resulting in inefficient operation.
In recent years, in a certain case, the oil return operation may be performed based on the oil level detected through an additional oil level sensor mounted in the compressor casing. The oil level sensor as described above may have the effect of reducing the number of unnecessary oil return operations, thus decreasing energy consumption and increasing the compressor operation time. However, material property (capacitance) is changed according to a refrigerant state and the mixture ratio of oil and refrigerant, such that it becomes difficult to correctly detect the oil level.